Heat vulcanizable rubber compositions comprising rubber components which have double bonds and are in the liquid or solid state at room temperature, vulcanizing agents which are in the solid state at room temperature, and vulcanizing accelerators which are in the solid state at room temperature are used in various fields of adhesives, sealants, coating materials, and also molded articles.
When such compositions are used for the production of vulcanized rubber molded materials, kneading for about one hour in the molding process generates mixing heat (to about 60.degree. C.), and causes a scorching problem due to the decomposition of the vulcanizing agent and vulcanizing accelerator by the mixing heat. To prevent such scorching, it is unavoidable to continuously carry out the molding process so that the composition can be quickly transferred to the molding step after the addition of the vulcanizing agent and vulcanizing accelerator. Furthermore, the amounts of the vulcanizing agent and vulcanizing accelerator should be adjusted in accordance with external atmospheres, in particular, temperature, to prevent the scorching problem.
When such compositions are used as adhesives or sealants, the rubber components, which are in the liquid state at room temperature, are used, or they are supplied in a paste state by dissolving them in plasticizers or the like. In such a case, when the composition is prepared in the form of a one pack type by the addition of the vulcanizing agent and vulcanizing accelerator to the rubber component, the vulcanization often proceeds gradually to form a gel during the storage until the use at around 40.degree. C. in the summer season. In this case, the heat vulcanizable rubber compositions are supplied in the form of a two pack type.
Accordingly, for the purpose of preventing scorch in the molding process for the production of vulcanized rubber molded articles, or ensuring the storage stability of the one pack pasty compositions, new components such as premature-vulcanizing-preventing agents (retarders), effective stabilizers, and vulcanizing agent or vulcanizing accelerators having good stability have been developed. However, none of them can achieve the above purpose satisfactorily.
Therefore, it is desired to develop a composition which is a one pack type one containing such a vulcanizing agent and a vulcanizing accelerator, and which does not start a vulcanization due to mixing heat, that is, which can prevent scorching, and thus has good storage stability.